1. Statement of the Technical Field
The invention relates to a non-contacting thermal rotary joint. More particularly, this invention relates to a non-contacting thermal rotary joint for transferring heat from heat generating devices disposed on a first substrate to a second substrate wherein the first substrate is rotatably mounted to the second substrate.
2. Background of the Invention
There are many applications where it is desirable or essential to transfer heat from a first substrate to a second substrate. The first substrate could have heat generating devices disposed thereon which generate heat which must be removed. It is desirable to transfer the heat to the second substrate which is disposed adjacent to the first substrate. The second substrate could be further thermally coupled to a heat sink for removing the heat from the second substrate.
In such applications, pin heat exchangers, liquid cooling, thermoelectric devices and/or heat pipes could be used to transfer the heat from the first substrate to the second substrate. Another example is found in U.S. Pat. No. 5,948,689 where there is provided a thermal coupling between a heat source and a heat sink comprised of an integrated interleaved-fin connector. A first substrate includes a first side surface and a second side surface. A plurality of heat generating devices are formed in the first side surface. A plurality of first channels are etched in the second side surface to form a plurality of first fins. A second substrate has a plurality of second channels etched therein to form a plurality of second fins and a base. The base is for thermally engaging with a heat sink. The first and second fins provide a thermally conductive path from the heat generating devices to the heat sink when interleaved with each other.
There are also many applications where it is desirable or essential to transfer heat from a first substrate to a second substrate across a rotary joint. For example, a satellite antenna typically includes several electronic components disposed on the rotating turntable supporting the antenna. The electronic components consume electrical power and generate heat which must be removed from the turntable or else the electronic components could be damaged. Since the turntable must rotate to align the antenna with a communications satellite, it can be difficult to remove the heat from the turntable. It is desirable to transfer the heat to the base which the turntable is rotatably mounted on. The satellite antenna could be located at a ground station, on a vehicle such as a truck, a ship, or an airborne vehicle such as an airplane, space vehicle, or satellite.
Another example of an application where it is desirable to transfer heat across a rotating joint includes a robotic arm and deployment mechanisms used in space. One or more electronic components mounted on a rotary substrate located at the distal end of the robotic arm generate heat which must be removed from the substrate. However, these examples are not meant to be limiting as there are may other applications known to one of ordinary skill in the art wherein it is desirable to transfer heat from a first substrate to a second substrate across a rotary joint.
It is known to use liquid rotary unions to transfer heat from a first substrate to a second substrate across a rotary joint. Drawbacks to the use of liquid rotary unions for this purpose are that they have a finite life, induce friction, and stiction and risk potential leaks which are particularly undesirable for satellite antennas such as small, precision antenna tracking positioners. Convection and radiation fins could be used but are limited in their effectiveness and efficiency in dissipating heat. The aforementioned thermoelectric devices and heat pipes have been considered but are not capable of transporting heat across a rotating joint. Moreover, thermoelectric devices can be used with a slip ring but at an increased size, weight, and cost.
In view of the forgoing, there remains a need for a device that can transfer heat from a first substrate to a second substrate across a rotary joint. In addition, such a device must be enduring, have low friction across the rotary joint, and reduce the stiction and leak risks making the device suitable for use in satellite antennas including small, precision antenna tracking positioners.